The present invention relates to a waste heat recovery system for an internal combustion engine, particularly to a waste heat recovery system, to which Rankine cycle is applied, for recovering waste heat of the internal combustion engine that generates at least two, first and second raised temperature portions by operation, a degree of raised temperature being higher at the first raised temperature portion than at the second raised temperature portion.
A known waste heat recovery system of this type is described in Japanese Patent Application Laid-Open No. 6-88523.
However, in the conventional device, raised temperature cooling water after cooling an exhaust port of an internal combustion engine is introduced into a heater provided in an exhaust pipe to generate vapor, and thus has a problem that heat of an exhaust gas having lower temperature than the raised temperature cooling water is disposed of without being recovered in the heater, thereby reducing a waste heat recovery rate.
The present invention has an object to provide a waste heat recovery system for sufficiently recovering waste heat from at least two raised temperature portions generated in an internal combustion engine by operation, efficiently converting recovered heat energies to mechanical energies, and integrating the mechanical energies to be output.
To attain the above described object, the present invention provides a waste heat recovery system for an internal combustion engine, to which Rankine cycle is applied, for recovering waste heat of the internal combustion engine that generates at least two, first and second raised temperature portions by operation, a degree of raised temperature being higher at the first raised temperature portion than at the second raised temperature portion, wherein the device includes: evaporating means having at least two, first and second evaporating portions, the first evaporating portion generating a first vapor with raised temperature by using the first raised temperature portion, while the second evaporating portion generating a second vapor with raised temperature by using the second raised temperature portion and with a lower pressure than the first vapor; an expander having at least two, first and second energy converting portions, the first energy converting portion converting an expansion energy of the first vapor introduced from the first evaporating portion into a mechanical energy, while the second energy converting portion converting an expansion energy of the second vapor introduced from the second evaporating portion into a mechanical energy, and both mechanical energies being integrated to be output; a condenser for liquefying the first and second vapors, which are exhausted from the expander, with dropped pressure after the conversion; and a supply pump for supplying liquid from the condenser to the first and second evaporating portions, respectively.
Configured as described above, waste heat can be sufficiently recovered from each raised temperature portion of the internal combustion engine and integrated to produce relatively high output. The expander in this case may be either of displacement type or non-displacement type.
According to the present invention, there is provided a waste heat recovery system for an internal combustion engine, to which Rankine cycle is applied, for recovering waste heat of the internal combustion engine that generates at least two, first and second raised temperature portions by operation, a degree of raised temperature being higher at the first raised temperature portion than at the second raised temperature portion, wherein the device includes: evaporating means having at least two, first and second evaporating portions, the first evaporating portion generating a first vapor with raised temperature by the first raised temperature portion, while the second evaporating portion generating a second vapor with raised temperature by using the second raised temperature portion and with a lower pressure than the first vapor; a displacement type expander having at least two, first and second energy converting portions, the first energy converting portion converting an expansion energy of the first vapor introduced from the first evaporating portion into a mechanical energy, while the second energy converting portion converting an expansion energy of the second vapor introduced from the second evaporating portion into a mechanical energy, and both mechanical energies being integrated to be output; a condenser for liquefying the first and second vapors, which are exhausted from the displacement type expander, with dropped pressure after the conversion; and a supply pump for supplying liquid from the condenser to the first evaporating portion and the second evaporating portion, respectively.
Configured as described above, the same operation and effect as described above can be obtained. For the displacement type expander, it has a wide rated operation area, so that even if flow rates of the vapors in the first energy converting portion and the second energy converting portion vary with variation in temperature at the first raised temperature portion and the second raised temperature portion in the internal combustion engine, the expander efficiently operates within a wide rotation area in proportion to the flow rates of the vapors, and integrates both mechanical energies of the first energy converting portion and the second energy converting portion to be efficiently output. On the other hand, since the non-displacement type expander has a narrow rated operation area, it is difficult to efficiently operate within a wide rotation area in accordance with variation in flow rates of the vapors. Thus, to efficiently operate the non-displacement type expander, the flow rates of the vapors are to be controlled within a range suited for the rated operation area. In this view, as an expander, the displacement type one may be suitable.